Subclinical autonomic disturbances in multiple sclerosis

We compared results from non-invasive autonomic testing [sympathetic skin responses (SSR), heart beat variation during deep breathing, and orthostatic manoeuvre with transcranial Doppler monitoring in 22 patients] with motor and somatosensory evoked potentials (MEP and SEP) in 30 unselected patients with multiple sclerosis. We found a similarly high yield of pathological results for SSR, MEP and SEP (66.7%, 65.5%, and 69%, respectively). When analysed for each limb (n = 120), SSR were highly correlated with MEP and SEP (for both P < 0.001). Heart beat variation was reduced in only 3 patients. In 4 of 22 patients orthostatic manoeuvre induced a pathological decrease in cerebral blood flow velocity despite normal systemic blood pressure being maintained. We conclude that SSR may be a useful additional diagnostic tool in patients with multiple sclerosis. Cerebral dysautoregulation is a rather frequent finding, although its significance is not known.